Improvement in the manufacture of white lead



H. J- OVERMAN'N.

Making Whitg Lead.

No. 59,135. v Patented -Oct. 23, 1866.

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UNI ED STATES PATENT OFFIon.

H. J. OVERMANN, OF NEW YORK, N. Y., ASSIGNOR TO WM. S. HASCALL, OF

' SAME PLACE.

IMPROVEMENT IN THE MANUFACTURE OF W HIT;E LEAD.

Specification forming part of Letters Patent No. 59, 135, dated October 2 1866.

To all whom it may concern Be it known that I, H. J. OVERMANN, of the city and county and State of New York, have invented a certain new and useful Improve ment in the Manufacture of White Lead and I do hereby declare that the following is a full, clear, and exact description thereof, reference being had also to the accompanying drawing, forming part of this specification, and consistin g of only one figure, which represents avessel made according to one part of my invention. My invention consists in a new and improved method of making white lead by chemical process, including, also, an improvement in the vessel or vessels in which the process is carried on.

In carrying out my invention, I use either the meta-l lead in the forms in which it is usually furnished, or litharge or ores of lead.

When ores of lead are used, I crush and roast them in the usual way in order to remove the sulphur. When the metal lead is used, I first reduce it to a fine condition, using for that purpose any suitable means, mechanical or otherwise, so that the lead shall not be in large solid masses, but shall be brought to a comparatively fine or reduced state, in order to increase as much as possible its exposed surfaces to the action of the solvents employed in the manufacture. This reduction to a fine state maybe effected by cutting or rolling the lead into thin sheets, and then cutting such sheets into narrow strips, and afterward dividin g the strips into small pieces, or by punching holes in or through sheets, bars, or masses of lead, or by shaving the lead into thin shavings or sheets, or by rasping it, so as to bring it into afine condition resembling metal filings; or the lead may be melted or heated red-hot, or nearly red-hot, and then poured into a body of water, when it will become porous and bulky and will present an increased surface to the action of the solvents used in the manufacture.

I take lead so reduced to a comparatively fine state, or so expanded by becoming porous or open, or made full of holes by punching, or in the form of litharge or of ore, and put it in a bath of dilute nitric acid for the purpose of dissolving it. The action of the acid in dissolving it maybe hastened by heating such acid and by stirring it occasionally.

When the lead has become dissolved I add to the solution a quantity of sulphuric acid sufficient to precipitate the lead, which settles to the bottom of the vessel in which the operations are conducted in the form of sulphate Y of lead.

As soon as the sulphate has settled I draw off the nitric acid, which can be used over and over again with fresh portions of lead or of litharge. I then wash the sulphate freely in the ordinary way until it is freed from acids. I then add pyroligneous or oxalic acid, or any similar acid, with or without tincal, or borax, or its equivalent, dissolved in water, in order thereby to destroy the crystalline structure of the sulphate and bringitto a finer condition sufficient water hein g added to allow these agents to be well diffused and to become intimately mixed with the sulphate.

I hasten the process by applying heat and by stlrring and agitating the-mass, either by using stirrers or by agitating the vessel, or both. The quantity of pyroligneous or oxalic or other similar acid used is about three to four per cent. by weight of the sulphate, and I use, also, about the same quantity of tincal or borax. These proportions may, however, be varied without departing from the principle of my invention,

If it is found that the pyroligneous or other acid and the borax are too much weakened by the water employed, a greater quantity of each can be taken.

The time required for destroying the crystalline structure of the sulphate is usually from two to'four hours, the time being less when heat is applied than when it is not applied.

The lead is next dried in flat pans, trays, or dishes subjected to heat, when it is ready for use.

The operations of dissolving the lead or lith arge, and of precipitating it, and of washing to free it from acids, and of stirring it in con tact with pyroligneous or similar acid, with or without tincal, or borax, or its equivalent, may be performed in the same vessel or in different vessels. Such vessel or vessels may be.

or" stone or other substances which will best resist the action of acids, or they may be made of wood or iron or other cheap material, and lined with sheet-lead of any desired thickness. hen the lining of lead has become worn away and dissolved by the acids used in the manufacture, so as to require renewal, a new lining can be placed therein at a small expense. By using vessels made in this way, with a lining of lead, I avoid the danger of discoloring and deteriorating the white lead by the ad dition of foreign substances, and also diminish the cost of the vessels in which the manufacture is carried on.

The size of the vessel or vessels may be sufiicient to dissolve one or more tons of lead or litharge at a single operation.

The lining of the operating vessels may be made of thick sheets of lead, so as to last the longer. It results from this mode of making the operatin g vessels that the wastage of their linings becomes added to the mass of white lead contained in such vessels.

Instead of preparing metal lead as above described for the action of the solvent, it may be taken in thin sheets and set edgewise near to each other in the operating vessel, and the acid be drawn off at the bottom every few hours, and fresh acid supplied from time to time, until the sheets of lead are dissolved.

Instead of first dissolving and then precipitatin g the materials in two distinct operations, the solvent and the precipitant may be put together in the right proportions in one vessel, and the lead or other material may be submitted to their action, keeping the whole well stirred, under the influence of heat, until the sulphate is deposited or precipitated. This method of conducting the operation ec0nomizes time, labor, and vessels.

By puttin g the nitric and sulphuric acids or other solvent and precipitant together in a vessel lined with lead, and leaving them therein for a period of several hours, a coating or deposit of sulphate of lead will be formed on the lining, which will preserve the said lining more or less from the action of nitric acid or other solvent in the future operations, and consequently the expense of renewal will be greatly lessened.

What I claim, and desire to secure as mystructure of the precipitated sulphate of lead, v

with or without the use of borax or its equiv-. alent, substantially as described.

3. In the manufacture of white lead, dissolving and precipitating lead or its compounds at the same operation in one vessel, the solvent and precipitant being first put together in such vessel, substantially as described.

H. J. OVERMANN.

Witnesses:

J. VAN SANrVooRn, Geo. F. SOUTHERN. 

